Superconductive magnetic separator



March 31, 1970 J. D. BANNISTER SUPERCONDUCTIVE MAGNETIC SEPARATOR 2Sheets-Sheet 1 Filed Aug. 5, 1968 M Ua w un MP M U WP FIG. 4

//v VEN TOR 1.2 BANN/STER ATTORNEY J. D. BANNISTER SUPERCONDUCTIVEMAGNETIC SEPARATOR March 31 1970 Filed Aug. 5, 1 968 2 Sheets-Sheet 2 RDu U L S ENTRANCE IN VENTOR J. D. BANN/STER 8V ATTORNEY United StatesPatent O 3,503,504 SUPERCONDUCTIVE MAGNETIC SEPARATOR John D. Bannister,Summit, N.J., assignor to Air Reduction Company, Incorporated, New York,N.Y., a corporation of New York Filed Aug. 5, 1968, Ser. No. 750,162Int. Cl. H01f 7/22; B03c 1/02 U.S. Cl. 209-223 20 Claims ABSTRACT OF THEDISCLOSURE System employing a superconducting magnet for separatingmagnetic and nonmagnetic components. A preferred embodiment takes theform of an ore separator in which the magnetic element is a thin panelof normally conducting material which encloses an array of superconductive magnetic coils. The panel is maintained at cryogenictemperatures by liquid helium circulating between the coils. A rotatingdisk serves to move a. slurry comprising magnetic and nonmagneticcomponents adjacent to the magnetic panel, where the magnetic componentsare deflected by the magnetic field, permitting the nonmagnetic gangueto move out through one exit channel. The magnetic components clingingto the disk are subsequently moved out of the magnetic field by furtherrotation of the disk, and are washed oif of the disk and removed througha separate exit channel.

BACKGROUND OF THE INVENTION This relates in general to magneticprocessing of minerals, and more particularly to the separation ofweakly magnetic constituents from a slurry containing mine tailings.

Various techniques using conventional iron core magnets have long beenemployed to separate magnetic minerals from the gangue. In currentpractice, for example, taconite ore is crushed and wet-ground to form aslurry from which the strongly magnetic fraction comprising magnetite ispicked up by low intensity magnetic separators, which may, for example,be rotating drums containing conventional magnets of either electric orpermanent types having fields within the range 600 to 900 gauss. Thenonmagnetic gangue and weakly magnetic iron constituents are discardedin the tailing.

Conventional magnetic separators function inadequately for thereclamation of the weakly magnetic ores from the tailings, so that thelatter are economically lost. The reasons for this are as follows.Conventional magnetic separators have the inherent disadvantage of beinglimited to field strengths of about 20,000 gauss, which is the limit ofthe magnetic saturation of the iron core required to control the field.Because of this, the maximum field strength attainable with iron-coremagnets is strictly limited, and the gap between the pole pieces of themagnet is necessarily narrow, restricting the volume of material siftingthrough, and leading to clogging.

Accordingly, it is the principal object of the present invention tosubstantially improve the magnetic processing of minerals, particularlythe weakly magnetic types, by the employment of super-magnets of a typenot heretofore used for this purpose.

More specific objects of the invention are to provide high intensitymagnetic separators which are characterized by substantially increasedspace for processing material subject to the magnetic field, thusaccommodating a greater volume flow of material with less clogging.

A further object is to provide a magnetic separation system havingbetter dynamics of the slurry stream then prior art processes.

Brief description of the invention These and other objects are achievedin accordance with the present invention in a device employing one ormore superconducting coils for the magnetic processing of minerals, moreparticularly weakly magnetic minerals such as are usually discarded inthe tailings of magnetic separators of the prior art types. Such adevice may take the form of a panel comprising a superconducting coil orcoils sandwiched between parallel plates of normally conductingmaterial, forming a closed segment in which the coil or coils aremaintained in a cryogenic environment. Ore containing weakly magneticconstituents passes in a slurry past the faces of the panel. The weaklymagnetic constituents are attracted to and held adjacent the panel bythe magnetic lines of force emanating from its face. The concentratedmagnetic ore is later removed from the magnetic field by mechanicalmeans, while the residual gangue passes from the device with the slurry.

In accordance with one embodiment of the invention, the superconductingmagnetic panel takes the form of a segment of a circular disk,comprising a pair of parallel copper face plates enclosing between theman array of small superconducting coils. These coils are formed fromsuperconducting wire or ribbon, mounted in a regular array, and woundand energized in such a manner that the field strength and fieldgradient of the panel are maximized in the area over the slurry channel.The superconducting panel is enclosed in a hollow disk-shaped chamberwhich rotates about a central axial hub with respect to the magneticsegment. The ore bearing slurry is passed in a thin layer over bothsides of the rotating disk-shaped chamber. The weakly magnetic ore isattracted to and held on the rotating disk by the force-field emanatingfrom the magnetic panel. The disk then rotates the concentratecomprising ferromagnetic material out of the magnetic field, where it isremoved from the disk by a wash stream.

In preferred form the superconducting coils in the magnetic panel, whichare formed from ribbon comprising a deposited layer of Nb Sn, arerefrigerated to about 42 Kelvin by liquid helium piped to the panelthrough the hub of the disk. Inside the magnetic panel, the liquidhelium is circulated between the pancake-shaped coils of superconductingribbon which are mounted on copper supports connected between the copperface plates. The coils are conduction-cooled by the liquid heliumflowing in channels. The coils are insulated from the environment byseveral layers of superinsulation which serves to support the evacuatedinterior of the panel against the external pressure. The vacuum pumpinglines and electrical connections to the magnetic panel pass through thehub of the disk. It is contemplated that the size and eifective magneticfield volume of this embodiment of the invention can be extended byusing several magnetic segments in parallel on the same hub.

It has been estimated that, using the invention in the form of thepreferred embodiment, operating on taconite tailings from which themagnetite fraction has already been removed, 60% recovery of theiron-bearing minerals can be obtained from a tailings stream inconcentration.

Although a specific form of the invention described by way of example,hereinafter, relates to the separation of the magnetic fraction from thetailings of taconite ore, it is anticipated that the invention has manyadditional applications in other mineral operations in both metallic andnon-metallic industries. A few examples are recovery of red mud (bearingiron ore) from bauxite processing, the treatment of molybdenum ores, thetreatment of nickel ores, the beneficiation of glass sands, and thebeneficiation of clay for use in the paper, rubber, and potteryindustries.

A particular advantage to be realized in the use of the presentinvention is that higher magnetic fields, of the order of several tensof kilogauss and higher gradients can be generated with superconductingmagnets. Moreover, the use of superconductive coils makes practical theemployment of large numbers of small magnetic coils in a panel array,further increasing the field strengths and gradients available using thepresent invention over those available using prior art iron coremagnets. Further, the use of air-core magnets, as opposed to iron-coremagnets, removes the field strength limitation imposed by the magneticsaturation of the iron core. This permits wider spacing adjacent themagnetic panel, thereby substantially increasing the rate at whichmaterial can be sifted through the apparatus without substantialclogging, and facilitating the processing of fine-ground material.

In the specification and claims hereinafter, the term superconductor isapplied to certain metals whose electrical resistance vanishes at atemperature known as the critical temperature, which is a function ofthe specific superconducting material, and which up to the present timehas not been known to exceed about 20 Kelvin. A material which cannot berendered superconducting at a given reference temperature, and whichconducts normally at the temperature, is known as a normally conductingmaterial. The phenomenon of superconductivity, including the propertiesand characteristics of superconductors, together with definitions andexplanations of the foregoing terms and others used by those skilled inthe art to describe their behavior, is set forth in detail in theliterature and in textbooks, including, for example, Superconductivityby C. A. Lynton, published by Methuen & Co. Ltd., 1962.

Other objects, features, and advantages of the invention will beapparent from a study of the specification hereinafter with reference tothe attached drawings.

Short description of the drawings FIG. 1 is a showing in cross sectionof a magnetic ore separator in accordance with the present invention;

FIG. 2 is a showing in side section along the line 2-2 of the oreseparator of FIG. 1;

FIG. 3 is an enlarged cross sectional showing of a stationary hollowsector 15 of FIG. 1;

FIG. 4 is a side sectional showing of the stationary hollow sector 15 ofFIG. 3, along the line 44 of FIG. 3;

FIG. 5 is a further enlargement, in cross-section, of a portion of theinner magnetic panel 19 of FIG. 3; and

FIG. 6 is a side sectional showing of the portion of the inner magneticpanel 19 shown in FIG. 5, with one of the copper cover plates removed.

Detailed description of the drawings The principles of the presentinvention can best be described with reference to the specificembodiment shown in cross-section and side section in FIGS. 1 and 2,respectively, which is designed to operate on the tailings of aconventional taconite ore separator. The drawings are intended forpurposes of illustration and are not to scale. For processing by thelatter, the ore has initially been crushed and wet-ground to form aslurry, from which a fraction comprising largely magnetite has beenseparated out by low intensity magnetic separators. These separators(not shown) are rotating drums containing conventional magnets, ofeither electric or permanent types, having fields which are ofcomparatively low intensity, of the order of 600 to 900 gauss. Thenonmagnetic gangue and weakly magnetic iron, including hematite andsimilar iron metals from the taconite processing, are descarded in thetailings.

The system of FIGS. 1 and 2 includes a cylindrical drum 1 in which ismounted a rotating disk-shaped chamber 2, the periphery of which movesbetween the upper slurry entrance 3, in which the tailings of thetaconite separator are received in a moving stream, and a pair of exitchannels 4 and 5, where the magnetic residue and the gangue are drawnoff separately. The heart of this system is a stationary sector 15including an inner magnetic panel 19 which is mounted inside of the disk2 in such a manner that it remains in a stationary position in theright-hand lower quadrant during rotation of the disk. Sector 15comprises a hermetically sealed, evacuated chamber enclosing aninsulated cryogenic environment in which is mounted an array ofsuperconductive coils 16 in a panel 19 of normally conducting material(see FIGS. 3 and 4). The coils are disposed to generate a magnetic fieldhaving lines of force which are substantially normal to the plane ofrotation of disk-shaped chamber 2.

Referring in detail to FIGS. 1 and 2 of the drawings, housing 1 is ahollow cylindrical drum comprising, for example, a steel shell /2 inchthick, having an abrasion resist-ant inner coating of hard rubber or thelike 0.2 inch thick. The housing 1, in the present illustrative example,forms a cylindrical inner cavity 12 feet in diameter and 4 inches deep,except for the centrally disposed hub portion 12 which is 1 foot indiameter and 4 feet deep. The housing 1 includes an entrance channel 3which projects upwardly in a direction approximately tangential to thecurved upper periphery of the housing 1. Channel 3 provides an elongatedrectangular mouth of 1 ft? cross sectional area designed to accommodatethe infiowing stream of slurry. Leading out of the lower end of housing1 are a pair of channels, including one ore exit 4 for the magneticresidue, and a gangue exit 5. The latter, approximately the same size aschannel 3, is centered at an angle of about moving in a clockwisedirection around the periphery of the housing from the center of theslurry entrance 3. Exit 5 projects out in nearly a radial direction fromthe housing, and is designed to be in nearly a straight-line path belowthe slurry entrance 3. The ore exit chanel 4, approximately the samesize as the others, is removed around the periphery of the housing 1 ina clockwise direction so that its center line forms an angle of about 45with that of the gangue exit 5.

Mounted inside of the cylindrical housing 1 is a disk shaped chamber 2,formed, for example, of a thin shell of hard rubber, or alternatively,hard rubber on a steel shell, or the like. Chamber 2 is 11 feet 9 inchesin inner diameter and 2 inches across the interior. At its center, it isshrunk onto two axial steel hollow drive shafts 2a, 2b, each 9 inches indiameter and having a Mr inch wall thickness. Shaft 2a extends 6 inchesout from the center of the left-hand face of disk-shaped chamber 2, andshaft 2b extends 12 inches out from the center of its right-hand face.Projecting drive shafts 2a, 2b are mounted to revolve, causingdisk-shaped chamber 2 to rotate about the short axis through its center.The drive shafts 2a, 2b may ride, for example, between systems of ballor roller bearings 7a, 7b and 7c, 7d, respectively, which arerespectively interposed between the inner wall of housing 1 and theouter surfaces of shafts 2a, 2b, and between their inner surfaces andthe outer surface of bearing pipe 11. The latter is of stainless steel,6 inches in diameter, having a wall inch thick, projecting an axialdistance of, say, 16 inches in each direction from the longitudinal axisof the disk 2.

Sealing means 8a, 8b are interposed between the bearings 7a, 7b and 7c,7d and the drive shafts on each side, to seal the interior chamber ofthe housing 1 and to protect the bearing 7 from the abrasive slurry.This may take the form, in each case, of a mechanical seal, well knownin the art.

Disk 2 is disposed to revolve about the axis at its center by means of adrive sheave 6, which is fixed to the right-hand end of the hollow driveshaft 2]) The drive sheave 6 is connected through a conventional systemof gears (not shown) to a conventional motor drive (not shown), whichdrives the disk 2 to rotate clockwise, in the present model, at a rateof, say, 16 revolutions per minute, so that the peripheral portion ofthe wheel moves at a linear velocity of about 5 feet per second,comparable to the rate of flow of the slurry in entrance channel 3, aswill be discussed hereinafter.

Inside of the revolving disk-shaped chamber 2 is fitted the stationaryhollow sector 15, which is shown in detail in cross and side section,respectively, in FIGS. 3 and 4, and which is a salient feature of thepresently described embodiment. Hollow sector 15, which is shaped tofill approximately one quadrant of the disk-shaped cham ber 2, thelatter revolving freely with respect to it, comprises a stainless steelouter shell having walls .040 inch thick. These enclose a chamber,rectangular in cross-section. 1 /2 inches across the interior, 5.5 feetalong each of the radial edges, and feet, approximately, along theperipheral edges, defining a pair of matched semicircular sector platesa and 15b, disposed with their principal surfaces parallel to eachother. The inner edge of the hollow sector '15 is centered on aninwardly curved closure plate 11a formed of stainless steel /2 inchthick, which is 6 inches across and extends about 90 around the interiorof the pipe 11 (see FIG 1). The closure plate 11a includes a pluralityof openings into which are hermetically sealed conduits for evacuatingthe hollow inner space of sector 15, conduits leading to and returningfrom a source of liquid helium, and conduits leading to and returning toa source of power, as will be explained hereinafter.

Symmetrically positioned inside of the outer shell provided by hollowsector 15, is an inner magnetic panel 19 formed of normally conductingmaterial which is de signed to accomodate in sandwich fashion an arrayof superconductive coils 16. On the exterior, panel 19 is shapedsimilarly to hollow sector 15, but somewhat smaller, comprising a pairof panel plates 19a and 1% which are 5.4 feet on each of their radialedges, 9.5 feet around the periphery, .250 inch thick, and spaced withtheir inner surfaces .1 inch apart.

The space between the outer shell comprising walls 15a, 15b of thehollow sector 15 and the parallel inner plates 19a, 19b of magneticpanel 19 is filled with superinsulation 18 which may comprise, forexample, sheets of aluminized Mylar .(Registered trademark of E. I. duPont de Nemours & Co.) film, having a thickness of, say, /2 mil, tightlypacked together. In addition to insulating the inner space, this servesto hold the inner chamber 19 in place, and keeps the hollow sector 15from collapsing. The hollow sector 15 is evacuated to a pressure of,say, 10* millimeters of mercury through a duct 17 leading to a vacuumpump 17a, and is then hermetically sealed.

Plates 19a and 19b, and the closed ends of the inner panel 19, areformed of copper inch thick. For preferred operation, this may comprisea copper manufactured by the American Metal Climax Company under thetrade name OFHC brand copper, of which the analysis is specified on page6 of their brochure entitled OFHC Brand Copper at Work, a case book ofapplications, Amex Publication OF/66-2780. The copper, in a preferredembodiment, should have a resistivity ratio within the range 100:300,where the ratio represents the resistivity at room temperature dividedby the resistivity at 42 C. It will be understood that other normallyconducting materials, such as, for example, aluminum, or alternatively,gold or silver, are useful for the purposes of the present invention,instead of, or in addition to, copper. The function of the normallyconducting panel 19, in addition to providing a mounting for thesuperconductive coils 16, is to prevent instability in thesuperconductive coil due to what is known in the art as flux jumping.

Referring again to FIGS. 3 and 4, one of the enclosing A inch thickcopper inner shell plates 19a, 19b, which are fastened together in apress fit, is removed to reveal an ordered array of pancake-shapedsuperconducting coils 16. Each pair of coils 16 is mounted on one of thecopper posts 16a, which pass through the thickness of the inner shell19a, 19b, the ends being integrally fixed in the panel sidewalls. Thisis more clearly shown in FIGS. 5 and 6 which are detailed showings ofthe arrangement of the coils 16 in the magnetic panel 19. In the presentexample, coils 16 which are 2 inches in diameter and .1 inch thick, aremounted in rows as shown in FIGURES 3, 4, 5 and 6 of the drawings,parallel to each of the radii of the quadrant sector. In the presentexample, each of the coils is formed of ribbon comprising a thin film ofsuperconducting material such as, for example, Nb Sn or niobiumtitanium, which has been diffused onto a substrate. This may comprise astainless steel or Hastalloy (registered trademark of Union CarbideCorporation) substrate, /2 mil thick and .05 wide and having a silvercoating, processed to form superconductive ribbon in the mannerdescribed in detail, for example, by E. R. Schrader and E. Kolondra inan article entitled Analysis of Degradation Effects in SuperconductiveNiobium Stannide Solenoids, RCA Review, vol. XXV, September 1964, andwhich is known as RCA Development No. R-602l4 Niobium-tinSuperconductive Ribbon.

A portion of the panel array of FIGS. 3 and 4, including thepancake-shaped coils 16 of superconductive ribbon, mounted on copperposts 16a and arranged in regular rows, is shown schematically in detailin the enlarged cross section in FIG. 5, and in the enlarged sidesectionin FIG. 6 of the drawings. The coils are set in double layered pairs,the winding in each case being from the center outward, with cross-overfrom one layer to the other being made at the center post 160, the twoends being wound clockwise and counterclockwise, respectively, to formthe upper and lower coils. Alternate coils are wound in oppositedirections, the electrical cross-over being made from one pair of coilsto the next, at the periphery of the first upper layer coil, and at theperiphery of the next under layer coil, etc.

All of the coils are connected in series to minimize the currentrequirement of the power supply and supply busses. The coils areconnected in rows, and crossovers from row to row are made at alternateends of the rows. The coils are wound in a manner to give a pattern ofalternate north and south poles on each face of the panel, which willgive the maximum magnetic force field over the volume of the slurrypassage.

It will be noted that the force on a weakly magnetic particle in amagnetic field is defined by the following equation:

F =kVHdH/ dy where: F=force k=volume susceptability of particle V:particle volume H=field strength, and

dH/dy :field gradient It will be seen by reference to FIG. 6 that adirect current of, for example 300 amperes passes from the 3 watt sourceof power 24 through the input trunk lead 21, traverses theseries-connected circuits in the panel 19, and returns to source 24through trunk conduit 22. The potential drop between the input conductor21 and output conductor 22 is, for example, 0.01 volt. Starting fromtrunk line 21, the current traverses the first pair of coils, passingdownward through the thickness of the panel, and in a reverse direction,returning upward through the thickness along the next pair of coils. Inthis manner, the current conducting path proceeds down one row of coils,and back the next, the last coil of the last row being connected to theoutput through the trunk line 22. In the example under description, thefiow of current generates in panel 19 a high intensity magnetic field ofthe order of 35 kilogauss through the thickness of the copper panel,providing areas alternately poled positive and negative, so that thepanel is characterized by areas of steep field gradient.

To provide the proper cryogenic environment for energizing thesuperconductive coils 16, the channels between the coils are filled withcirculating helium brought into panel 19 through conduit 1411 (see FIGS.3 and 4) from the source 27, which includes a compressor for providing astream of helium at a pressure of 16 pounds per square inch absolute anda temperature of about 4 Kelvin, flowing at the rate of 15 gm./sec.Conduit 14a is surrounded by a vacuum-insulated pipe. The liquid heliumis vaporized as it flows through the channels surrounding the coils 16,returning as gas through the pipe 14b to the compressor connected tohelium source 27.

In operation, the separator works as follows. After the initial step inwhich the magnetite fraction of the crushed taconite ore has beensubstantially removed from the slurry by conventional magneticseparators (not shown), the tailings from these separators, includingnonmagnetic gangue and weakly magnetic iron having a high component ofhematite, serve as the raw materials for the separator disclosed inFIGS. 1 and 2 herein.

The slurry, as it flows into the intake channel 3, is about solid in awater carrier, of which about 9% is weakly magnetic material, includingmostly hematite, and the remainder of which is nonmagnetic ganguge. Theaverage particle size is about .375 inch. The slurry flows into theentrance pipe 3 at a mass flow rate of about 10 cubic feet per second,and at a linear velocity of about 5 feet per second, falling in asubstantially even stream on the outside edges of revolving disk-shapedchamber 2, being carried partly by gravity and partly by rotation of thedisk to gangue exit 5. Since the latter is located in nearly a straightline path directly below the slurry entrance 3 it is in a position toreceive the nonmagnetic gangue which falls off of revolving disk 2. Asthe slurry reaches the area adjacent the magnetic segment 15, themagnetic material, including the hematite component, is drawn by thehigh intensity force field, which extends from the front to back face ofthe panel 15, and clings to the outside of the rotating disk 2. Therotation of the hollow rubber disk 2 removes the clinging magneticmaterial beyond the effective field of the magnetic sector to a pointbeyond the exit channel 5 and adjacent the exit channel 4 where one ormore high velocity streams of water are directed against the face of therevolving disk 2, disengaging the weakly magnetic residue, whichsubsequently flows out through the channel 4 where it is collected forfurther processing. Salient characteristics of the disclosedillustrative embodiment are given in Table I.

TABLE I Characteristics of illustrative ore separator of presentinvention Slurry channel on each side of the panel:

Depth-inches 1.0 Panel area-square feet 24 Superconducting magnet, coilsper square foot 9 Magnetic field (on a coil centerline):

At the panel-kilogauss 35 At one inch from the panel-kilogauss 7 Slurryspeedfeet per second 5 Estimated concentrate output at:

60% recoverytons per hour 27 60% recovery-tons per year (235,000)

The figures in Table I are based on a number of simplifying assumptions.In the illustrative separator the magnetic force on a hematite particleis estimated at 100 times the force on a magnetite particle in aconventional separator. Use of this high force-field creates thepossibility of collecting gangue with the concentrate. Thus, a usefulseparation in accordance with the principles of the present inventionmay involve multiple stages of weaker force fields. While the ratio offorces on particles of low but differing susceptibilities is constantwith increasing field strength, the difference between these forcesbecomes larger and allows for easier adjustment of the separationparameters to effect a separation. Clearly, any given separationrequires empirical adjustment of the number of stages, the slurryconcentration, the particle velocity, the channel depth and length, andthe force-field strength. It is conceivable that in some practicalapplications, separation may require stronger fields or more stages thandisclosed herein, resulting in an increased superconducting ribbonrequirement.

It will be apparent that the embodiment under description should beconstructed to insure long-term reliability under very strenuousmechanical service. In particular, the problem of maintaining structuralintegrity while passing the very abrasive slurry as close as possible tothe coil windings is paramount.

Although the invention has been described with reference to a specificembodiment for separating hematite and weakly magnetic ore from thetailings of a taconite separation system, it will be understood that theprinciples of the invention have much broader application, and that theparticular materials and forms of the components disclosed may bechanged to meet the specific necessities of each application. Moreover,the present inventive concept of employing a superconductive magneticsystem for the purposes of separating out ferromagnetic material fromnon-magnetic material is not restricted to constructions employing anarray of small magnets of the type shown by way of illustration; but, itis within the contemplation of the invention that for certain types ofembodiments a single large magnetic configuration employing theprinciples of superconductivity may be preferable.

It will be understood by those skilled in the art that the scope of thepresent invention is not restricted to the particular structures and/ orparameters disclosed herein by way of illustration; but, that the scopeof the invention is defined in the appended claims.

I claim:

1. A system for separating out desired magnetic components from materialcontaining a mixture of magnetic and non-magnetic components, saidsystem comprising an entrance channel for accommodating a moving streamof said mixture and a plurality of separated exit channels comprising afirst exit channel accommodating streams comprising primarilynon-magnetic components and a second exit channel for accommodating thedesired magnetic components of said mixture, a source of electricalpower, circuit means in energy transfer relation with said sourceconstructed to generate a magnetic field between said entrance and exitchannels in the path of said moving stream for diverting the desiredmagnetic components in said stream from entering said first exitchannel, said circuit means including superconducting material arrangedin an array of superconductive coils having their major faces aligned insubstantially the same plane, all of said coils being interposed in apanel of normally conductive material, means comprising a cryogenicenvironment for bringing said superconductive material to a temperaturebelow its critical temperature, and means for removing said divertedmagnetic components from the effective area of said magnetic field to anarea adjacent said second exit channel and for deflecting said magneticcomponents into said second exit channel.

2. The combination in accordance with claim 1 wherein each of said coilsis mounted on an axis of normally conducting material.

3. The combination in accordance with claim 2 in which saidsuperconductive coils are pancake-shaped windings formed of ribbonscomprising a nonsuperconducting substrate having a superconducting layerdeposited on one face of said substrate.

4. The combination in accordance with claim 3 wherein said normallyconductive panel is essentially copper, and said superconducting layercomprises a principal component of Nb Sn.

5. The combination in accordance with claim 1 wherein said panel isinterposed in a hermetically sealed chamber and said means forestablishing a cryogenic environment includes a source of liquid heliumand channel means connected to said source and respectively passingthrough said chamber and said panel adjacent said coils to deliverliquid helium to said coils, and further channel means for withdrawinghelium gas formed in said panel, said chamber including insulating meansadjacent said panel.

6. The combination in accordance with claim 1 wherein said meanscomprises a device rotatable in a plane substantially transverse to thedirection of said field for removing said magnetic components to an areaadjacent said second exit channel, and means for directing a highvelocity stream of liquid onto the face of said device in a positionoutside of said field for Washing said magnetic components into saidsecond exit channel.

7. A magnetic separator comprising in combination, a housing includingan entrance for accommodating a slurry comprising magnetic andnon-magnetic components, said housing including a pair of exitscomprising an ore exit and a gangue exit spaced apart in said housingfrom said entrance, a moving means constructed to traverse the spaceinterval between said entrance and each of said exits comprising arevolving disc, magnetic cans for deflecting the magnetic portion ofsaid slurry to one of said exits While permitting the non-magneticportion of said slurry to leave by the other said exit comprising astationary section adjacent said revolving disc and located to deflectthe magnetic component of said slurry from an area adjacent said gangueexit to an area adjacent said ore exit, said stationary sectorcomprising a hermetically sealed cryogenic system includingsuperconducting material in the form of a plurality of superconductingcoils disposed in an array between layers of normally conductingmaterial to form a panel disposed within said hermetically sealedcryogenic system, said array constructed and arranged to create amagnetic force field in a direction substantially normal to the plane ofrotation of said disc and means for maintaining said cryogenic system ata temperature below the critical temperature of said superconductingmaterial.

8. The combination in accordance with claim 7 wherein alternate ones ofsaid coils are oppositely poled to produce a high field gradient betweeneach of said coils and the adjacent coils of said array.

9. The combination in accordance with claim 7 wherein said stationarysector comprises a closed panel of normally conducting materialincluding an array of coils formed of ribbon comprising asuperconducting film overlaid on a nonsuperconducting substrate, thesaid coils being mounted in a regular array on a series of supports ofnormally conducting material formed integrally with said panel.

10. The combination in accordance with claim 9 wherein said hermeticallysealed system includes a plurality of channels spaced apart adjacentsaid coils, a source of liquid helium, means for connecting said sourceto an intake point in said hermetically-sealed system, whereby saidliquid helium circulates through said chan- 10 nels, and an exit channelfor conveying said helium to return to said source.

11. The combination in accordance with claim 10 wherein saidsuperconducting film comprises primarily Nb Sn, and said normallyconducting material comprises primarily copper.

12. The combination in accordance with claim 10 wherein saidsuperconducting film comprises primarily niobium titanium.

13. The combination in accordance with claim 10 wherein said substratecomprises primarily stainless steel.

14. Apparatus for separating a desired magnetic component from a mixturecontaining both magnetic and non-magnetic components comprising, ahousing having an entrance for said mixture and a plurality of exits forthe removal of the desired magnetic component and the remainder of themixture; magnetic means for separating the desired magnetic componentfrom said mixture, said magnetic means comprising an inner panelcontaining a plurality of superconducting magnets within an outerevacuated chamber, means to supply liquid helium to said panel tomaintain the temperature of said magnets at or below the criticaltemperature, further means to Withdraw helium gas that is found in thepanel, said magnets comprising a plurality of superconducting coilsconnected in series and arranged to give a pattern of alternate northand south poles to establish a steep field gradient.

15. The apparatus of claim 14 wherein superinsulation is positionedaround the inner panel in said evacuated chamber.

16. The apparatus of claim 14 in which the magnetic means is located inclose proximity to a movable element in said housing and generates amagnetic field which passes through at least part of said element, saidmixture contacting said movable element as it passes through saidhousing.

17. The apparatus of claim 16 in which the movable element comprises adisk shaped chamber containing the magnetic means.

18. The apparatus of claim 14 in which the inner panel comprisesnormally conductive material.

19. The apparatus of claim 14 in which the coils are pancake shaped withsubstantially coplanar faces.

20. The apparatus of claim 14 in which the coils are formed about centerposts of normally conductive material.

References Cited UNITED STATES PATENTS 939,523 11/1909 Ludwick 209-223 X3,026,151 3/1962 Buchhold 335-216 X 3,157,830 11/1964 Matthias 335-2163,173,079 3/1965 McFee.

3,187,235 6/1965 Berlincourt 335216 3,200,299 8/1965 Autler 3352l6 X3,265,939 8/1966 Rinderer 335-216 3,281,737 10/1966 Swartz 335-2163,289,836 12/1966 Weston 209214 3,394,330 7/1968 Schindler 335-216 FRANKW. LUTIER, Primary Examiner U.S. Cl. X.R. 209-22 Column Column ColumnColumn Column Column Column Column Column Column Column Column Attest:

Patent No.

Inventor(s) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION JohnD. Bannister Dated March 3 97 It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

line 71,

line 1, line &9,

line 27, lines #0 line 71,

line 30, line 73,

lines 5 L line 16,

line 28,

line 3M,

Edward M. Fletcher, Ir. Attesting Officer "then" should read --than--.

heading should be all caps.

the word --the-- is missing between "in channels".

the word "the" should read --that--. and 55, headings should be allcaps. "descarded" should read -discarded--.

"one" shouldread --an--.

the period is missing at the end of sentence, after "2b" through 58should have been indented.

the comma is missing after "tion" the word "ganguge"should read-gangue--.

"section" should read --sector-.

SIGNEI sewn sips-1970 WILLIAM E- W, JR. Commissioner of Patents F ORMPO-1D5O 10-69)

